1. Field of Invention
The present invention relates to a projection display device, and more particularly, to a technique for efficiently cooling components arranged inside the device by using cooling air.
2. Description of Related Art
Hitherto, a projection display device has been known which includes a light-source lamp serving as a light source, an optical system for forming an optical image according to image information by optically processing a light beam emitted from the light-source lamp, a projection lens for enlarging and projecting the image formed by the optical system onto a projection plane, a power supply for supplying electric power for driving the device, and an intake fan and an exhaust fan for cooling the inside of the device.
Such projection display devices are widely used for multimedia presentations at conferences, academic meetings, exhibitions, and the like.
In such projection display devices, noise from the intake fan and the exhaust fan is a problem. On the other hand, the light source, the optical elements, and the like disposed inside the device may be deteriorated when the temperatures thereof exceed a predetermined temperature. Deterioration of these components results in reduction in image quality and the like, and this is undesirable.
One aspect of the present invention is to provide a projection display device in which such fan noise is minimized, and in which a light source, an optical element, and the like are prevented from deteriorating.
A projection display device of the present invention includes a light source; a modulation device for modulating a light beam emitted from the light source; a projection lens for projecting the light modulated by the modulation device onto a projection plane; a power supply for supplying electric power for driving the device; an exhaust fan for exhausting air inside the device; a power supply intake fan primarily for drawing in air for cooling the power supply; and a modulation device intake fan primarily for drawing in air for cooling the modulation device. The invention may provide that only the power supply intake fan is driven for a predetermined period after the device is powered on. According to this, for a predetermined period after the device is powered on, only the power supply intake fan, which must be cooled from the time of power-on, is driven, whereby fan noise can be reduced.
In the above-described projection display device, fan noise can be further reduced by rotating the power supply intake fan at a relatively low speed for a predetermined period after the device is powered on, and by rotating the power supply intake fan at a relatively high speed after the predetermined period has elapsed from the time of power-on.
In the above-described projection display device, when a rotation speed control device is provided to control the rotation speed of the exhaust fan, the rotation speed of the fan can be limited while the inside of the device is maintained at a relatively low temperature, which can reduce fan noise.
When a lens is placed in the optical path between the light source and the modulation device, it is preferable that the rotation speed of the exhaust fan be controlled based on a detected temperature from a first temperature detecting device for detecting the temperature in the vicinity of the light source, or a detected temperature from a second temperature detecting device for detecting the temperature in the vicinity of the lens. This makes it possible to prevent the light source and the lens from deteriorating, and to thereby prevent reduction in image quality.
In this case, it is preferable that the light source be extinguished when the detected temperature from the first temperature detecting device, or the detected temperature from the second temperature detecting device continues to be higher than a predetermined preset temperature for a predetermined period. This makes it possible to reliably prevent the light source and the lens from deteriorating.
Furthermore, after the light source is extinguished, a kickback phenomenon sometimes occurs in which the detected temperature from the temperature detecting device rises although the temperature inside the device is actually low. Therefore, if the light source is extinguished the moment the detected temperature exceeds the predetermined preset temperature, it may not be possible to relight the light source later even though the temperature inside the device is actually low. In contrast, when the light source is extinguished when the detected temperature remains higher than the predetermined preset temperature for the predetermined period, the light source can be relighted even when the detected temperature from the temperature detecting device is higher than the predetermined preset temperature. That is, according to such a configuration, it is possible to prevent the relighting of the light source from being hindered by the kickback phenomenon.
Furthermore, in the projection display device of the present invention, the rotation speed of the modulation device intake fan can be limited while the inside of the device is maintained at a relatively low temperature, by providing a rotation speed control device for controlling the rotation speed of the modulation device intake fan, which can reduce fan noise.
In this case, it is preferable that the rotation speed of the modulation device intake fan be controlled based on a detected temperature from a third temperature detecting device for detecting the temperature in the vicinity of the modulation device, or a detected temperature from a fourth temperature detecting device for detecting the temperature of outside air. This makes it possible to prevent the modulation device from deteriorating, and to thereby prevent reduction in image quality.
Furthermore, in this case, it is preferable that a preset temperature for changing the rotation speed of the modulation device intake fan be varied in accordance with the detected temperature from the fourth temperature detecting device. There is a small difference between the detected temperature from the third temperature detecting device for detecting the temperature in the vicinity of the modulation device, and the actual temperature of the modulation device. Therefore, if the rotation speed of the intake fan is controlled only by the third temperature detecting device, it may be insufficient, even though cooling efficiency for the modulation device must be increased in practice. In contrast, when the preset temperature for changing the rotation speed of the modulation device intake fan is varied in accordance with the detected temperature from the fourth temperature detecting device, it is possible to control the rotation speed of the modulation device intake fan in a more suitable state, and to more reliably prevent the modulation device from deteriorating.
In this case, it is preferable that the light source be extinguished when the detected temperature from the third temperature detecting device, or the detected temperature from the fourth temperature detecting device remains higher than a predetermined preset temperature for a predetermined period. This makes it possible to prevent the relighting of the light source from being hindered by the kickback phenomenon described above.